Minimally invasive surgical robotic systems are being developed to increase surgeon's dexterity when working within an internal surgical location. Such minimally invasive procedures are conducted by inserting surgical instruments through small incisions on the skin of the patient. The use of dexterous surgical instruments to manipulate tissues and suture would facilitate the performance of an endoscopic surgical procedure. A manually or robotically actuated surgical device that can articulate as well as actuate reliably would minimize patient risk and operating time.
Current minimally invasive surgical tools have many drawbacks. Most endoscopic tools have rigid shafts and are constrained to approach the workspace from the direction of a small incision. In addition, many robotic devices often have their motors or actuators mounted on the adjacent links. When these motors are mounted on moving links, their weight often reduces the performance of the device. Sometimes the volume that motors occupy near the end-effector can interfere with the access to a workspace. Furthermore, the construction and length of many endoscopic instruments reduces the surgeon's ability to feel the force exerted by tissues and organs on the end-effector. The limited dexterity and sensitivity provided by endoscopic tools is a major obstacle to the improvement and expansion of minimally invasive surgery.
Surgical tools that increase the surgeons' dexterity are needed to improve minimally invasive surgery procedures. It is desirable to provide surgical instruments having a wrist with two or tree degrees-of-freedom. It is further desirable to provide a wrist mechanism that has low friction in order to provide the surgeon with sensitivity feedback of the contact forces exerted by the surgical tools. Furthermore, it is desirable to minimize the stretch in a cable operatively coupling a portion of the tool that is inserted through the incision with power and control mechanisms that remain outside the incision.